Catchment to coast: fishes of the Keurbooms–Bitou system, Western Cape Province, South Africa

Abstract

The Keurbooms–Bitou is a fynbos and forested catchment that has no major impoundments and provides a perennial high-quality water supply to the downstream estuary. This review collates the fish species occurrence results from a single comprehensive survey of the Keurbooms–Bitou catchment and estuary, together with past occurrence information, thus providing a more comprehensive context in terms of a comparison between freshwater and estuarine fish species richness. Altogether, a relatively low species richness (7 indigenous taxa) in the Keurbooms–Bitou catchments was documented when compared to the much higher species richness (41 indigenous taxa) in the estuary. The high proportion of indigenous freshwater-associated (57%) and estuary- associated (54%) endemic species in the two major aquatic habitats underlines the overall importance of this system to fish assemblages in the southern Cape. However, if only the 1994–1996 fish survey results are used as the historical baseline, then a total of 8 fish species (7 indigenous taxa) were recorded in the Keurbooms–Bitou River catchment and 28 species (17 endemic taxa) in the Keurbooms–Bitou Estuary. Using all estuarine datasets, at least 21 marine fish species are dependent or partially dependent on the estuary for healthy adult populations along this coast.